The present invention relates to a pavement marking system comprising a pavement surface and, adhered to the pavement surface are multiple layers of marking stripes comprising a first marking stripe comprising a solidified thermoplastic resin comprising a black pigment and, adhered to said first marking stripe, a second marking stripe comprising a thermoplastic resin comprising a pigment that visibly contrast with the first marking stripe. More particularly, the present invention relates to a durable pavement marking system comprising a pavement surface and, adhered to the pavement surface multiple layers of marking stripes comprising a first marking stripe that is from about 40 mils to about 110 mils thick comprising a solidified thermoplastic resin comprising a black pigment and, adhered to said first marking stripe, a second marking stripe that is from about 40 mils to about 750 mils thick comprising a thermoplastic resin comprising a pigment that visibly contrasts with the first marking stripe. Because of the color contrast and the thickness of the first and the second marking stripe, the pavement marking system remains highly visible during daylight hours and in rainy periods.
Traffic marking paints for use on pavement, such as road surfaces, are important elements in modern traffic direction and control. They have been used, for example, in the form of arrows and lane dividers, as parking lot striping, to designate special areas, e.g., handicapped parking, and the like and are typically applied directly to the pavement surface. These paints are subject to a variety of factors that require their reapplication. For example, abrasion from high traffic volume can result in frequent reapplication of the traffic markings. Weathering, i.e., rain or snow, and high and low ambient temperature effects can melt, crack or decompose the traffic marking material rendering it ineffective for the purpose intended.
In addition to the factors associated with durability and environmental stability, these paints also require rapid drying rates, since traffic disruption is an important consideration in the selection of a traffic marking paint. It is important to minimize the time for vehicles to drive over the paint without smearing, smudging or removing the paint.
An alternative to paints has been the use of tapes that employ an adhesive to bond the traffic marking tape to the pavement. See for example Lasch et al, U.S. Pat. No. 5,536,569. However, the adhesive material of these tapes is disadvantageously sensitive to high and low ambient temperatures and other weathering conditions. Further, because they do not readily conform to the numerous imperfections in pavement surface, their full adhesiveness to such surfaces is imperfect. Automobile tires distort these tapes, pulling and even tearing them from the road surface.
Recently, the use of thermoplastic-based compositions have been developed that offer several advantages over the typical traffic paint compositions. For example, see U.S. Pat. Nos. 3,996,645 to Okazaki et al, 4,713,404 to Cavitt, 6,020,073 to Wilson and 6,107,367 to Lazarus et al.
Thermoplastic traffic marking materials are typically applied by melting the composition and then applying the molten composition to the road surface. The temperature of the composition when being applied to the road surface is above 350xc2x0 F. and, if applied in a thin enough layer, will cool sufficiently rapidly without spreading. These present-day, thin-layer, thermoplastic marking materials suffer from a lack of durability. However, the application of a single stripe of over 0.150 inch to provide enhanced durability but which typically has a tendency to spread during the application process, has been proposed. See U.S. Pat. No. 5,511,896.
It is well known that water does not drain from conventional road marking stripes during wet weather conditions. Because a thin film of water forms on the top of the traffic stripe during such rain event, the retroreflectivity of glass beads (used to enhance visibility of the road marking) is significantly reduced. In fact, in heavy rains, the retroreflectivity is entirely destroyed because of such film of water. In order to provide increased visibility of the road marking stripes, large reflective elements are used that extend above the water film. Further, thicker stripes have been proposed that project above the water film.
A problem also exists with visibility of pavement markings on light colored pavements. This is particularly a problem with white pavement markings on concrete. Because of the lack of contrast in color between the pavement surface and the marking material. A contrast base color marking has been used to improve daytime visibility with preformed tapes such as disclosed in U.S. Pat. No. 5,298,761, for example. However, the positive effect of this application is limited due to the fact that the contrast colored area is limited to a relatively narrow strip on each side of the white marking. there exists no contrast colored area in front of or behind the colored markings. This provides little improvement in daytime visibility.
There have also been attempts to provide contrast markings using black traffic paint as the contrast color base. However, traffic paint markings are very thin, typically between about 5 to about 7 mils. As such, they have very limited durability, e.g., about 6 months or less. This limited durability results in ineffective markings over time or very frequent reapplication of the pavement marking causing unacceptable increases in labor costs and disruption of traffic. The very thin application of traffic paint does not extend the marking stripe sufficiently above the pavement surface to produce a visible stripe during wet weather conditions.
A need exists for pavement marking stripes that have enhanced day time visibility on light colored pavement surfaces and during periods of wet weather.
The present invention is directed to an improved thermoplastic pavement marking composition system that comprises a pavement surface. A first marking stripe is applied and adheres to the top of the pavement surface. This first marking stripe has a thickness of at least about 40 mils to about 110 mils, and comprises a solidified thermoplastic resin composition. The solidified resin composition comprising a black pigment. A second marking stripe is applied and adheres to the surface of the first marking stripe, the second marking stripe having a thickness of at least 40 mils to about 750 mils. It is narrower than said first marking stripe and comprises a solidified thermoplastic resin composition. The thermoplastic resin composition is comprised of a pigment that visibly contrasts with the first marking stripe. Because of the high contrast in color between the two stripes and the light colored pavement surface, the markings are highly visible in daytime conditions. Additionally, because of the thickness of each of the stripes as well as the combined thickness of the stripes, the marked pavement system is highly visible during periods of rain.
A third marking stripe, narrower than the second marking stripe and identical in color and thickness to the first marking stripe, may be applied to the second marking stripe. Similarly, a forth marking stripe, narrower than the third marking stripe and identical in color and thickness to the second marking stripe, may be applied to the third marking stripe. The stripes may be repeated numerous times.